Bluedharma wrote:
I was reading the story by Tony Samuelson, that he posted regarding his adventures in a two seat spit in 1968-1969.
http://www.samuelson.co.uk/blog/?p=70#more-70But I am somewhat confused by his statements.
Tony Samuelson wrote:
You have to fly a Spitfire to understand what the feeling is when you are taking off. I only ever did it once for real but the sensation is unforgettable. The Merlin engine is supercharged and it is necessary to pull full power to get the aeroplane off the ground. Getting the undercarriage up so that you can reduce the power is a top priority because twelve pounds of boost, which is the figure that comes into my mind, is only ever used in combat and, after five minutes of that, the engine has to be thrown away. As it speeds up along the runway the plane wants to yaw to the left and to compensate the pilot has to boot the right rudder with all his might. (Or it may be right yaw and left rudder. This is thirty years ago.). Meanwhile the engine is screaming and flames are belching from every exhaust port.
But on page 22 of the Spitfire IX, XI & XVI notes it says:
Quote:
39. Take-off
At training and normal loads + 7 lb./sq.in. to + 9 lb./xq.in. boost is sufficient for take-off. After take-off, however boost should be increased (where applicable) to + 12lb./sq.in. to minimize the possibility of lead fouling of the sparking plugs.
You don't have to throw the engine away after five minutes of 12...Right?
He also says engines last about 200 hours. They last longer than that??? don't they?
Cheers.
Yes, that puzzled me too!
Whilst you can of course go up to +12 for take off, I think you'll find that most operators of todays aircraft (usually at lighter weights than when in service) use a max of around +8 for the MKVIII/IX/XVI, as that is quite sufficient, and helps with the torque & prop effects, making the take off a bit more managable!
I know there's has always been a debate amongst pilots & the maintenance men regarding full power use at take off on these big engines, but it would seem that the use of a figure lower then +12 at take off is acceptable, as can be seen from the pilots notes.
As for Merlin engine overhaul life, I thought that most of todays owners/operators look to achieve about 500 hrs.
Cheers
Paul